Using a Classroom Computer as Screen and Keyboard

The first requirement is that the RealVNC Viewer be installed on the classroom computers that will connect to the Raspberry Pis.  This may be a job for your school's information technology staff depending on how your classroom computers are configured and managed.  You can download the RealVNC viewer for free, for Windows, MacOS, and Linux.  It's available in the Apple App Store for the iPad and in the Google Play Store for Android tablets.  If your school uses Chromebooks, the process may be more complex.  Instructions on how to use RealVNC on a Chromebook can be found on the RealVNC website.  If your Chromebooks will run Android apps, be sure to see the note at the bottom of that page.

You will assign a name to each Raspberry Pi.  Make them short, like "pi01" and "pi02" and so on until you've named all of them.  The names should start with a letter and then contain only letters or digits.  Use lowercase letters.  With a label maker or just a pen, make labels small enough to stick on top of the Ethernet jack.  (Writing directly on the jack with a felt-tip doesn't work; it rubs off easily.)

The real magic comes from configuring the DHCP (dynamic host configuration protocol) and DNS (domain name system) servers.  Every network device has a built-in identifier called a MAC address.  (That's short for medium access control.)  You will need to know the MAC addresses of each Pi; they're all unique.  You can do that by opening a terminal window and typing ip link show followed by the enter key.

The screenshot shows typing the command and a sample result.  To find the MAC address for the wireless adapter, look for wlan0.  In that group of data, look for link/ether. The MAC address is six pairs of hexadecimal digits separated by colons, shown in the third circled item in the screen shot.

Make a list of each Pi, its name, and it's MAC address, like this:  pi01 dc:a6:32:f3:73:46

You, your IT staff, or perhaps the district IT staff, can use that list to configure DHCP so that it assigns an IP (Internet Protocol) address to each Pi when it's started up and associates the correct name with each pi. 

The other part of the magic is something called the domain suffix search list.  If a name with no dots is entered into an Internet address, the operating system tries to resolve an address by appending a suffix from the domain suffix search list.  For example, if your school is schoolhouse.k12.us, that first Pi might have an address of pi01.schoolhouse.k12.us, but we want the students to be able to type just "pi01."  That will work if the domain suffix is set to "schoolhouse.k12.us." Some browsers send a string that doesn't look like a complete URL off to a search engine. There's often a configuration setting to prevent that. Adding "http" should also work, like http://pi01.

It might happen that your school doesn't have its own domain name.  That's the case with the Cobb County School District, for example; all the schools are in the cobbk12.org domain.  If two schools in a district set up that way each name their Raspberry Pis pi01, etc, there will be name conflicts.  The solution is to use subdomains.  Continuing with the Cobb example, we might have pi01.tapp.cobbk12.org and also pi01.mceachern.cobbk12.org.  Presto!  No more name conflict.  Of course, the domain suffix search list must now contain an entry with the subdomain.